This invention relates to disc handling, retrieval, and storage devices.
The technique of storing information on a diskette, cassette, or other storage unit has long been known. For example, a musical selection may be recorded in a groove on a vinyl disc and replayed by conventional phonographic techniques. Other examples include 8 track and cassette tapes, floppy discs or diskettes, and hard disks for storing digital data in a magnetic form which can be read with appropriate magnetic sensors. More recently, optical and capacitive discs have been developed which store information in a form which can be retrieved optically or capacitively. The optical disc are sometimes referred to as laser discs because they can be read with light emitted by a laser, or they are referred to as a compact disc because of the amount of information that can be stored on a single, relatively small disc. Because of the information storage capacity of optically based digital data available on discs, it has become feasible to store both audio and video information on a disc.
The audio compact disc is a rigid plastic disc of about 4.7 inches in diameter with a concentric 0.06 inch diameter hole. Video discs can be larger, and other types of discs vary in size from these two types. Also in use today are optically based disc systems for use as digital storage devices for computers, known as CD ROM devices, where CD ROM stands for compact disc read only memory. Further, recordable discs are available which can be written to. In addition to audio and video information, data discs have been used to store many types of information including encyclopedias, scientific monographs, catalogs of books, old news reels, and collections of raw data to name only a few. All of these types of discs will be referred to herein as data discs or simply discs.
A single sided data disk can store over 1 gigabyte of data. Therefore, systems have been developed allowing more than one user to access information on a single data disc. Some data disc systems are available that access multiple data discs. For example, up to a dozen or so compact discs are loaded into a magazine, which is then inserted into a disc player. When a data disc is selected for retrieval or play, a loading mechanism loads the data disc onto the play mechanism or disc drive of the disc player. When another data disc is selected, the first disc must be unloaded from the disc drive and reinserted into the magazine before the next data disc can be loaded into the disc drive.
Other systems have been provided where multiple disc drives are available to access and play multiple discs for different zones or output terminals. The automated systems currently available for storing and retrieving data discs have, however, been subject to certain limitations and disadvantages.
Space for storage of data discs is one consideration. Even though the data disc can store an extremely large amount of information, it is easy to build a large library of data discs. A large library of music data discs, for example, is quickly collected. In the past, the discs have been handled inside of caddies which are enclosures with a movable door to allow access to the disc. The caddie is typically six times the thickness of a disc. Thus, eliminating caddies is a significant advancement. Systems for the storage, retrieval, handling, and play of music data discs in multiple juke boxes, even if a caddie is not used, are large and bulky and, thus, have little application in private homes in which items larger than stereo components are undesirable. Further, available commercial systems for the storage, retrieval, and handling of data discs are too large to fit in standard size commercial component racks.
Storing discs close enough together to reduce the size of the system creates difficulty in handling the discs. For example, there is not enough room to securely grasp the discs, and positioning the disc accurately for placement in a small storage area requires fine adjustments. Consistent retrieval and replacement of data discs from and into a storage area small enough to substantially reduce the size of a system, has not been obtained. At times, discs are only partially inserted into a storage position. The internal moving parts, usually a disc transport assembly, of the system then strike the disc and damage or break it.
This problem is accentuated by orienting the disc drives differently then the storage rack, so that the discs must be rotated or turned relative to the storage and play orientations of the discs. Rotating the data discs requires extra space and increases the possibility of slight errors in placement. Handling discs in a horizontal plane also increases the possibility of slight errors in placement because gravity acts downwardly on the disc to remove the disc from the horizontal place. Movement of the storage rack in which the data discs are stored can also introduce error into disc placement. Moving such a relatively large mass having a relatively large inertia makes it difficult to finely adjust the position of the discs. Further, movement of the storage rack reduces the speed at which discs can be accessed because the heavy rack cannot be subjected to high acceleration, and the rack must be repositioned for the retrieval of each disc.
Thus, increasing the number of data discs storable in a given area and the consistency of retrieval and placement of data discs is desirable to make data disc storage, retrieval, and handling devices more reliable and feasible for home and public use.